[OkayPhysicist]

I've played a few video games with this model: the source being available is a help to modders and the like, while still maintaining the game's commercial status. The best example I can think of is Barotrauma, where just a couple months ago there was a release that subtly broke networking on Macs. Quick code change fixed it so that my Apple-locked friends could play until the company got around to fixing it. Minecraft falls into the sorta-defacto version of this, where they distribute the necessary mappings to decompile the game for modding purposes.

Personally I think it should be the default distribution model for software. If I'm relying on a piece of software, especially one I paid for, doubly-especially if it's running on my machine, I should have the right to modify it and probably to distribute my modifications.